1. Field of the Invention
The present invention relates to a portable telephone with a moving status detection function, and in particular to a movement detection technique of determining by the portable telephone itself whether it is at rest or moving at high speeds during incoming call reception operation.
2. Description of the Prior Art
With the recent widespread use of portable telephones, it is observed now and then that use of portable telephones gives neighboring persons trouble depending on the using environment. It is also known that use of the portable telephone during driving of a car may cause a traffic accident. It is therefore required that one should observe the rules of etiquette and secure the safety at the time of using the portable telephone during driving of the car or in a train.
Japanese Patent Laid-Open No. 10-224856 discloses an example of mobile communication terminal equipment designed to observe such etiquette. The mobile communication terminal is provided with a reception electric-field intensity detector and a fading pitch detection circuit that determines from the reception electric-field intensity whether a moving speed of the terminal exceeds a predetermined value or not. Then, a response controller determines whether the terminal is moving at high speed or not, based on a determination of the fading pitch detection circuit. When the determination of the response controller shows that the terminal is moving at high speed, the terminal automatically responds to an incoming call, sends a response message to the opposite party of the communication. And the terminal stores a message received from the opposite party in a memory.
Japanese Patent Laid-Open No. 10-157555 discloses another example of an apparatus with a function of calculating moving speed. In the portable telephone apparatus disclosed therein, a radio section detects a time variation of electric field intensity of a radio signal received through an antenna. Then, a computation section calculates the moving speed of the own portable telephone in the mobile unit based on this variation. And the computation section determines whether the portable telephone apparatus is being used in the running car or not, depending on this moving speed and regulates outgoing and incoming calls of the portable telephone apparatus based on the decision. Further, a location detection section detects the current location using radio waves from GPS (Global Positioning System) satellites. Then, the computation section calculates the moving speed of the own portable telephone apparatus in the mobile station based on this current location. And the computation section determines whether the portable telephone apparatus is being used in the running vehicle, based on this moving speed. Outgoing and incoming calls of the portable telephone apparatus are regulated based on the determination.
Japanese Patent Laid-Open No. 10-108263 discloses a similar prior art. In the radio communication apparatus disclosed therein, a received signal strength detector measures an RSSI value at predetermined intervals. The RSSI value takes a value corresponding to reception field intensity of a radio channel. The amount of variation of this RSSI is converted to the moving speed of the radio communication apparatus. And, whether the radio communication apparatus is traveling at low speed or at high speed is determined based on the moving speed. Outgoing and incoming calls of the radio communication apparatus are regulated based on the determination. And, therein, a method of reducing moving speed determination errors is disclosed. In the method, the radio communication apparatus is accumulating the amount of variation of RSSI a predetermined number of times or during a predetermined period of time. And the radio communication apparatus converts the amount of the accumulation to a velocity value.
Incoming call receiving operation sequence control of a portable telephone according to a prior art will be explained by referring to FIG. 1.
In FIG. 1, while the portable telephone is on standby waiting for communication, if a caller calls the portable telephone, then a call signal is sent to a base station (step a2). In response to the call signal, the base station sends a paging signal to the portable telephone (step b2).
The portable telephone receives the paging signal from the base station and analyzes it. The portable telephone determines whether the received paging signal is addressed to itself or not. When it is determined that the paging signal is addressed to itself, the portable telephone sends a radio status report signal as a response signal to the base station (step c2). Then, upon receipt of this radio status report signal, the base station selects a communication radio channel suitable for the portable telephone and sends a radio channel designation signal to the portable telephone (step d2).
Upon receipt of the radio channel designation signal, the portable telephone switches to the radio channel designated by the base station. And then, the portable telephone receives a call setup signal from the base station (step e2). When receiving the call setup signal, the portable telephone sends a call signal in response to the call setup signal to the base station (step f2). Upon receipt of the call signal from the portable telephone, the base station sends the caller side a ringing tone indicating that the portable telephone is being called actually (step g2).
Furthermore, the incoming call is displayed on a display device of the portable telephone. When the user takes the incoming call, the portable telephone sends a response signal to the base station (step i2). In response to the response signal, the base station sends a response acknowledgment signal back to the portable telephone (step m2). The above sequence allows voice communication between the portable telephone and the caller.
Such a portable telephone having a function of estimating the own moving speed is already known. However, estimation of the moving speed according to the prior art is performed at regular intervals. Therefore, the estimated moving speed does not always match the moving speed when an incoming signal is actually received. In other words, there is a possibility that the portable telephone may operate based on an incorrect estimation result. For example, the estimation may indicate that the portable telephone is not moving at high speed although the portable telephone is actually moving at high speed, and vice versa.
Furthermore, from the standpoint of the user of the portable telephone according to the prior art, it is necessary to preset functions adaptable to conditions during driving of a car before actually driving the car. For example, once the portable telephone is set to a mode of “during driving”, a ringing tone stops thereafter. Such a setting or cancellation of the setting is required at the start and end of driving of a car. Thus, if such a presetting that indicates “during driving” is not canceled, there may be cases where voice communication is prevented even if the user is actually not driving a car. The opposite case can also be occurred. In the case, a ringing tone may suddenly sound even if the user is actually driving a car and may provoke an operation error.